Installations for the coating of parts by powdering

ABSTRACT

A powdering enclosure shields the parts to be coated and powdering means. A distributing device is situated close to the powdering enclosure and connected to the powdering means. A recovery system treats the gas extracted from the powdering enclosure and an input system introduces into the distributing device a quantity of powder corresponding to a part of that delivered by said distributing device to the abovesaid powdering means. The recovery system comprises a battery of several separating cells traversed by the gas extracted from the powdering enclosure and arranged to retain the powder in suspension in this gas. A first set of valves enables the selective isolation of one at least of these calls. A second set of valves enables the purging of this cell by a neutral gas to clean the cell and to draw the powder in it to a recycling pipe ending at the distributing device. This recycling pipe is traversed by a neutral gas for the pneumatic transport of the powder coming from the cell. The input system comprises a powder reserve communicating with a supply pipe, ending at the distributing device, traversed by a neutral gas for the pneumatic transport of the powder coming from said reserve.

United States Patent n9 Ambry t 1451' Nov 12, 1974 1 1 INSTALLATIONS FORTHE COATING OF PARTS BY POWDERING [75] Inventor: Gerard Ambry,Fontenay-le-Flcury,

France [73] Assignee: Air Industries, Courbevoie, France [22] Filed: May10, 1973 [21] Ap pl. N0.: 358,955

[30] Foreign Application Priority Data Primary E.\'aminerW. C. ReynoldsAssistant ExaminerLeo Millstein Attorney: Agent, or FirmLarson. Taylor &Hinds [57] ABSTRACT A powdering enclosure shields the parts to be coatedand powdering means. A distributing device is situated close to thepowdering enclosure and connected to the powdering means. A recoverysystem treats the gas extracted from the powdering enclosure and aninput system introduces into the distributing device a quantity ofpowder corresponding to a part of that delivered by said distributingdevice to the abovesaid powdering means. The recovery system comprises abattery of several separating cells traversed by the gas extracted fromthe powdering enclosure and arranged to retain the powder in suspensionin this gas. A first set of valves enables the selective isolation ofone at least of these calls. A second set of valves enables the purgingof this cell by a neutral gas to clean the cell and to draw the powderin it to a recycling pipe ending at the distributing device. Thisrecycling pipe is traversed by a neutral gas for the pneumatic transportof the powder coming from the cell. The input system comprises a powderreserve communicating with a supply pipe, ending at the distributingdevice, traversed by a neutral gas for the pneumatic transport of thepowder coming from said reserve.

9 Claims, 1 Drawing Figure INSTALLATIONS FOR THE COATING OF PARTS BYPOWDERING The invention relates to installations for the coating ofparts by powdering, the parts thus coated with a layer of powder ofgiven thickness being then subjected to a suitable treatment to fix thispowder and to obtain an adherent protective coating.

In such installations, the powder is distributed into a powderingenclosure by powdering means generally constituted by one or severalelectrostatic installations spraying the powder, electrified in itspassage through said installations, on to the part which is then broughtto an electrical potential different from that to which the powder isbrought.

These powdering installations are connected to a distributing devicesituated close to the powdering enclosure, and they deliver a flow-rateof powder greater than that necessary for the coating.

The atmosphere of the powdering enclosure is constantly renewed byblower means and the gas extracted from said powdering enclosure isdirected towards a recovery circuit where all or part of the powdercontained in this gas is recovered.

Moreover, the installation comprises an input system enabling theintroduction into the distributing device of an amount of powdercorresponding to a part of that delivered by said distributing device tothe powdering I apparatus.

It is an object of the invention to improve installations of theaforementioned type,especially as regards the arrangement of therecovery circuit and of the input circuit.

The invention has a further object of improving these installationsespecially as regards the elimination of the risks of explosion and offire in the distributing device, in the recovery system, in the inputsystem and in the powdering enclosure proper.

The invention is applicable more particularly to installations intendedfor the automobile industry, the parts on which it is desired to obtaina protective coating being automobile bodies.

The installation according to the invention comprises a powderingenclosure shielding the parts to be coated and the powderingapparatuses, a distributing device being situated close to the powderingenclosure and connected to the powdering apparatuses, a recovery circuittreating the gases extracted from the powdering enclosure, and an inputcircuit introducing into the distributing device a quantity of powdercorresponding to a part of that delivered by the said distributingdevice to the abovesaid powdering apparatuses, and this in-' stallationis characterised by the fact that,

the recovery system comprises a battery of several separating cellstraversed by the gas extracted from the powdering enclosure and arrangedto retain the powder in suspension in this gas, a first set of valvesenabling the selective isolation of one at least of these cells, asecond set of valves enabling the injection into the cell thus isolatedofa neutral gas for purging this cell of the gas contained in it, whichcan be a fuel, to complete the I clearance and cleaning of this cell andto draw the powder retained in it cell towards a recycling pipe endingat the distributing device, this recycling pipe being tra-' versed by aneutral gas ensuring the pneumatic transport of the powder coming fromthe abovesaid cell,

and the input system comprises a reserve of powder communicating with asupply pipe ending at the distributing device, this supply pipe beingtraversed by a neutral gas providing for the pneumatic transportation ofthe powder coming from the abovesaid reserve.

lt will'then be seen that it is possible to arrange the powder reserverelatively far from the powdering enclosure, and, especially to renderthis powder reserve accessible to delivery vehicles or containers(lorries or special wagons equipped for the transportation ofpulverulent materials).

Moreover, the presence ofa neutral gas ensuring the entraining andtransportation of the powder enables the elimination of explosion risksin the distributing device, in the recovery system, in the input systemand in the powdering enclosure proper.

According to an advantageous feature of the invention, the neutral gas,for creating a non-explosive atmosphere in the isolated separation cell,circulates in the same direction as the powder carrier gas which haspassed through this cell, this in order to avoid any movement of thepowder before the atmosphere of the cell concerned has becomenon-explosive.

According to yet another advantageous feature of the invention, therecycling pipe and the supply pipe each comprise, in front of thedistributing device, a separating device in which the powder transportedis separated from the neutral gas passing through the abovesaidrecycling and supply pipes.

, The invention consists, apart from the features which have just beenconsidered, of certain other features which are preferably used at thesame time and which will be more explicitly considered below.

The invention will in any case be well understood by means of theadditional description which follows as well as of the accompanyingdrawing, which description and drawing relate to a preferred embodimentof the invention, and do not comprise of course any limiting nature.

The single FIGURE of this drawing is a diagrammatic view of a powderinginstallation constructed according to the invention.

This installation comprises a powdering enclosure 1, in whichthe partsto be coated 2, such as automobile bodies, are borne by a conveyor 3.

The powder is distributed into this powdering enclosure I by a powderingapparatus 4 which can be constituted by several electrostatic guns 4a,4b, 4c and 4d spraying the powder, electrified on its passage throughsaid guns, on to the part 2 which is then brought to a potentialdifferent from that to which the powder is brought.

These powdering apparatuses 4 are connected to a distributing device 5situated close to the powdering enclosure 1. v

The powdering enclosure 1 is supplied with clean gas through a blowerfan 6 introducing this clean gas into cent) of the flow-rate of powderdelivered by the powdering apparatuses occurs in the gas extracted fromthe powdering enclosure.

Under these conditions, there is provided a recovery system, denoted ina general way by the reference numeral 8, to treat the gas extractedfrom the powdering enclosure 1.

As for the distributing device 5, it cooperates with an input system,denoted in a general way by the reference numeral 9, this input system 9introducing into the distributing device 5 an amount of powdercorresponding to a part of that delivered by a said distributing device5 to'the powdering apparatuses 4.

The recovery system 8 comprises a battery of several separating cells10a, 10b, 10c traversed by the gas extracted from the powderingenclosure, and arranged to retain the powder in suspension in this gas.

The first set of valves 11a, 11b, 11c enables the isolation selectivelyat one at least of the cells 10a, 10b and 100 and a second set of valves12a, 12b, and 120 enables the injection into the cell thus isolated of aneutral gas for purging this cell of the gas that it contained and whichcan be a fuel, to complete the clearing and cleaning of this cell, andto entrain the powder retained in this cell to a recycling pipe 13ending at the distributing device 5, this recirculating pipe 13 beingtraversed by a neutral gas ensuring the pneumatic transport of thepowder coming from the abovesaid cell.

The neutral gas, intending to create a non-explosive atmosphere in theisolated separating cell, flows in the same direction as the carrier gasfor the powder which has traversed this cell, this in order to avoid anymovement of the powder before the atmosphere of the cell concerned hasbecome non-explosive,

The input system 9 comprises a reserve of powder 14 communicating with asupply pipe 15 ending at the dis tributing device 5, this supply pipe 15being traversed by a neutral gas ensuring pneumatic transport comingfrom this reserve 14.

The separating cells 10a, 10b, 10c are provided respectively, at theirlower part, with isolating valves 16a,

16b, 16c ending in a hopper l7 the powder coming from these cells beingdirected by gravity towards the recycling pipe 13 through a valve 18.

The powder is introduced into this recycling pipe 13 through a blowerdevice 19 in which the neutral gas mixes with the powderto therebyensure the pneumatic transport. i

The powder coming from the reserve 14 is directed by gravity towards thesupply pipe 15 through a rotary valve 20.

The powder is introduced into this supply pipe 15 through a blowerdevice 21 in which the neutral gas is mixed with the powder to ensurethe pneumatic transport thereof.

The neutral gas used is the same in the recovery circuit 8 and in theinput circuit 9 and nitrogen can advantageously be used. I

A bottle of compressed nitrogen 22 is therefore arranged to supply, onone hand, the recovery system 8, through a valve 23, and on the otherhand, the battery of separating cells 10a, 10b, 100, through a set ofvalves 12a, 12b, 12c. ln therecycling pipe 13 the neutral gas is placedin circulation by a fan 24 or a compressor of the ROOTS type, followedby a cooler 25.

For ease of installation there may be enclosure; an-.

other bottle of compressed nitrogen 26 to feed the supply system 9,through a valve 27.

One of these two bottles of compressed nitrogen, for example the bottle26, can also feed for their pressurisation, the reserve 14, thedistributing device 5, and a vehicle or a delivery container 28. One orseveral valves such as 29 can then be provided to control thesedifferent functions. In the supply pipe 15 the neutral gas is'placed incirculation through a blower 30 or a compressor of the ROOTS type,followed by a cooler 31.

The recycling pipe 13 and the supply pipe 15 each comprise, in front ofthe distributing device 5, a separating device, respectively 32 and 33,in which the transported powder is separated from the neutral gas bypassing through the abovesaid recycling l3 and supply 15 pipes.

The separating device 32 communicates with a hopper 34, situated in thedistributing device 5, through a valve 35, and the separating device 33communicateswith a hopper 36, located in the distributing device 5,through a valve 37.

The distributing device 5 is also provided with a third hopper 38 inwhich there may be introduced, through a valve 39, supplementarysubstances (dyes, consumable additives, etc.).

Downstream of the battery of separating cells 10a, 10b, 10c there areprovided an extraction fan 40 connected to the abovesaid cells by a setof valves 41a, 41b, 41c.

The powdering enclosure 1 being supplied with air, the circulation ofair is effected in open circuit, and the air recycling through theextraction fan 40 is ejected to the atmosphere, if necessary afterhaving been washed to eliminate the particules of residual powder.

1f the powdering enclosure 1 is supplied with neutral gas, thecirculation of this neutral gas is effected in closed circuit, and thegas recycled by the extraction fan 40 is brought back to the blower fan6 through a return circuit 42 (shown in mixed line), in which a washingdevice or powder remover 43 is arranged to remove the particles ofresidual powder.

The powdering enclosure 1 is generally provided with an upstreamante-chamber 44 and a downstream antechamber 45, the gas extracted fromthese two chambers 44 and 45 being discarded to the atmosphere, ifnecessary after having traversed a washing or powder removing device 46to eliminate the particles of powder which have accidentally passed fromthe powdering enclosure to one and/or other of these two chambers.

In the linking pipe 47 connecting the hopper 7 of the powderingenclosure 1 to the battery of separating cells 10a, 10b, 10c, there isprovided advantageously an injector device 48 through which neutral gascan be introduced into the pipe 47 in the form of two opposed jets. Thisintroduction is actuated by an electrovalve 49 connected to one orseveral fire detectors 50 arranged in the powdering enclosure 1.

Due to this arrangement, and when a shock wave (due to an explosion) ora light or infra-red radiation (due to slow combustion) is detected bythe one or more detectors 50 and the powdering enclosure 1, theelectrovalve 49 opens and a neutral buffer gas is admitted into the pipe47 between the powdering enclosure l and the recovery system 8comprising the battery of separating cells 10a, 10b, 100.

The spreading of the fire to this battery is hence avoided, taking intoaccount the amount of powder retained in the cells, which combines withthe air, the

necessary components for an explosive reaction.

Moreover, the rapid admission of neutral gas into the pipe 47 can be putto profit to actuate a valve device 51 placing this passage incommunication with the atmosphere and avoiding hot gases or even flames,from being aspirated to the extraction fan 40 and spreading the fire tothe battery of separating cells 10a, 10b, 100.

Finally and whatever the embodiment adopted, there is provided aninstallation which has a certain number of advantages among which may bementioned those summarized by the following points:

possibility of arranging the reserve of powder at a relatively distantpoint from the powdering enclosure, which enables this reserve powder tobe rendered accessible to vehicles and delivery containers, thisadvantage being particularly important when the consumption of powder ishigh, which is the case in installations intended for the automobileindustry;

considerable reduction in the risks of explosion and fire in thedistributing device, in the recovery system and in the input system, andthis by reason of the neutral gas which flows in these parts of theinstallation and which creates an inert atmosphere on clearing andcleaning of the separating cells (the most dangerous operation whichoccurs during the functioning of the installation);

the possibility of ventilating the powdering enclosure with a neutralgas, circulating in the closed circuit, which considerably reduces therisk of explosion and fire in the powdering enclosure the detection ofexplosions and of fires in the powdering enclosure and immediateisolation of the recovery system with respect to the powderingenclosure.

As is self evident, and as emerges already from the foregoing; theinvention is in no way limited to those of its types of application andembodiments which have been more especially envisaged; it encompasses,on the contrary, all modifications.

I claim:

1. Installation for the coating of parts by powdering, comprising apowdering enclosure shielding the parts to be coated and powderingmeans, a distributing device situated close to the powdering enclosureand connccted to the powdering means, a recovery system adapted to treatthe gas extracted from the powdering enclosure and an input systemadapted to introduce into the distributing device a quantity of powdercorresponding to a part of that delivered by said distributing device tothe abovesaid powdering means, in which installation:

the recovery system comprises a plurality of separating cellstraversible by the gas extracted from the powdering enclosure andarranged to retain the powder in suspension in this gas, a first set ofvalves enabling the selective isolation of one at least of I thesecells, a second set of valves enabling the injection into the cell thusisolated of a neutral gas for purging this cell of the gas contained init for completing the clearing and cleaning of this cell and to draw thepowder retained in this cell towards a recycling pipe ending at thedistributing device, this recycling pipe being traversible by a neutralgas for the pneumatic transport of the powder coming from said cell,

and the input system comprises a reserve for powder communicating with asupply pipe ending at the distributing device, said supply pipe beingtraversible by a neutral gas for the pneumatic transport of the powdercoming from said reserve.

2. Installation according to claim 1, arranged to circulate the neutralgas, for creating a non-explosive atmosphere in the isolated separatingcell, in the same direction as the carrier gas for the powder which hastraversed said cell, so as to avoid any displacement of the powderbefore the atmosphere of the cell concerned has become non-explosive.

3. Installation according to claim 1, wherein the recycling pipe and thesupply pipe each comprise, in front of the distributing device, aseparating device adapted to separate the transported powder from theneutral gas passing through said recycling and supply pipes.

4. Installation according to claim 1, comprising means for supplying thepowdering enclosure with air, the circulation being effected in opencircuit.

5. Installation according to claim 1, comprising means for supplying thepowdering enclosure with a neutral gas, and an extraction fan forextracting the neutral gas from the powdering enclosure situateddownstream of the battery of separating cells, and means forreintroducing the neutral gas into the powdering enclosure after it hastraversed a washing or depowdering device.

6. Installation according to claim 1, including an injection deviceprovided in the linking pipe connecting the powdering enclosure to theplurality of separating cells, and means for supplying said injectiondevice with neutral gas so as to produce in said pipe at least onegaseous jet to isolate said powdering enclosure from the recovery systemwhen conditions indicative of explosion or of combustion are detected inthe powdering enclosure.

7. Installation according to claim 6, wherein the connecting pipecomprises, between the injection device and the powdering enclosure, avalve device placing this connecting circuit in communication with theat mosphere when the injection device deliversits gaseous et.

8. Installation according to claim 1, including means adapted tocirculate the same neutral gas through the recycling system, saidseparating cells and the input system.

9. Installation according to claim 1, adapted to circulate a fuel gas assaid neutral gas.

1. Installation for the coating of parts by powdering, comprising apowdering enclosure shielding the parts to be coated and powderingmeans, a distributing device situated close to the powdering enclosureand connected to the powdering means, a recovery system adapted to treatthe gas extracted from the powdering enclosure and an input systemadapted to introduce into the distributing device a quantity of powdercorresponding to a part of that delivered by said distributing device tothe abovesaid powdering means, in which installation: the recoverysystem comprises a plurality of separating cells traversible by the gasextracted from the powdering enclosure and arranged to retain the powderin suspension in this gas, a first set of valves enabling the selectiveisolation of one at least of these cells, a second set of valvesenabling the injection into the cell thus isolated of a neutral gas forpurging this cell of the gas contained in it for completing the clearingand cleaning of this cell and to draw the powder retained in this celltowards a recycling pipe ending at the distributing device, thisrecycling pipe being traversible by a neutral gas for the pneumatictransport of the powder coming from said cell, and the input systemcomprises a reserve for powder communicating with a supply pipe endingat the distributing device, said supply pipe being traversible by aneutral gas for the pneumatic transport of the powder coming from saidreserve.
 2. Installation according to claim 1, arranged to circulate theneutral gas, for creating a non-explosive atmosphere in the isolatedseparating cell, in the same direction as the carrier gas for the powderwhich has traversed said cell, so as to avoid any displacement of thepowder before the atmosphere of the cell concerned has becomenon-explosive.
 3. Installation according to claim 1, wherein therecycling pipe and the supply pipe each comprise, in front of thedistributing device, a separating device adapted to separate thetransported powder from the neutral gas passing through said recyclingand supply pipes.
 4. Installation according to claim 1, comprising meansfor supplying the powdering enclosure with air, the circulation beingeffected in open circuit.
 5. Installation according to claim 1,comprising means for supplying the powdering enclosure with a neutralgas, and an extraction fan for extracting the neutral gas from thepowdering enclosure situated downstream of the battery of separatingcells, and means for reintroducing the neutral gas into the powderingenclosure after it has traversed a washing or depowdering device. 6.Installation according to claim 1, including an injection deviceprovided in the linking pipe connecting the powdering enclosure to thePlurality of separating cells, and means for supplying said injectiondevice with neutral gas so as to produce in said pipe at least onegaseous jet to isolate said powdering enclosure from the recovery systemwhen conditions indicative of explosion or of combustion are detected inthe powdering enclosure.
 7. Installation according to claim 6, whereinthe connecting pipe comprises, between the injection device and thepowdering enclosure, a valve device placing this connecting circuit incommunication with the atmosphere when the injection device delivers itsgaseous jet.
 8. Installation according to claim 1, including meansadapted to circulate the same neutral gas through the recycling system,said separating cells and the input system.
 9. Installation according toclaim 1, adapted to circulate a fuel gas as said neutral gas.